Queue management in a forwarder

ABSTRACT

A queue management method, system, and recording medium include Selective Acknowledgments (SACK) examining to examine SACK blocks of the forwarder o selectively drop packets in the forward flow queue based on a reverse flow queue and MultiPath Transmission Control Protocol (MPTCP) examining configured to examine multipath headers to recognize MPTCP flows and examine the reverse flow queue to determine if redundant data has been sent such that the dropping drops the redundant data.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation Application of U.S. patentapplication Ser. No. 15/689,103, filed on Aug. 29, 2017, which isContinuation Application of U.S. patent application Ser. No. 14/969,871,now U.S. Pat. No. 9,843,530 issued on Dec. 12, 2017, the entire contentsof which are hereby incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with Government support under W911NF-06-3-0001awarded by the Army Research Office (ARO). The Government has certainrights to this invention.

BACKGROUND

The present invention relates generally to queue management innetworking devices such as bridges, routers, and certain types ofnetwork function appliances, but not by way of limitation, to a system,a method, and a recording medium for queue management using informationcontained in packets traversing a reverse path from a forwarder tointelligently select which packets in queue to drop.

Many conventional techniques exist to manage queues in networks and arecategorized as Active Queue Management (AQM). The AQM techniques attemptto drop packets intelligently so as to improve throughput and reducedelay.

That is, conventional techniques include, for example, drop tail, RandomEarly Drop (RED), the proportional integral (PI) controller, StochasticFairness Queuing (SFQ), and Controlled Delay (CoDel). The common themein these techniques is that the techniques only consider informationrelated to simplex (single-directional) flows, such as queue length,arrival time, or packet markings.

Thus, the present inventors have recognized that the above conventionaltechniques, and other conventional techniques, are limited in theirapplications in that the techniques only utilize single-directional flowparameters to manage queues and do not consider information available inthe corresponding reverse flow as a way to determine which packets todrop. Thus, when forced to drop a packet, the conventional techniquesfrequently drop a useful packet instead of a redundant one.

SUMMARY

In an exemplary embodiment, the present invention can provide a queuemanagement system, including a queue examining device configured toexamine a reverse flow queue from a forwarder for an acknowledged packetand a dropping device configured to drop a packet in a forward flowqueue if the packet in the forward flow queue includes the acknowledgedpacket in the reverse flow queue.

Further, in another exemplary embodiment, the present invention canprovide a queue management method, including examining a reverse flowqueue from a forwarder for an acknowledged packet and dropping a packetin a forward flow queue if the packet in the forward flow queue includesthe acknowledged packet in the reverse flow queue.

Even further, in another exemplary embodiment, the present invention canprovide a non-transitory computer-readable recording medium recording aqueue management program, the program causing a computer to perform:examining a reverse flow queue from a forwarder for an acknowledgedpacket and dropping a packet in a forward flow queue if the packet inthe forward flow queue includes the acknowledged packet in the reverseflow queue.

There has thus been outlined, rather broadly, exemplary embodiments ofthe invention in order that the detailed description thereof herein maybe better understood, and in order that the present contribution to theart may be better appreciated. There are, of course, additionalexemplary embodiments of the invention that will be described below andwhich will form the subject matter of the claims appended hereto.

It is to be understood that the invention is not limited in itsapplication to the details of construction and to the arrangements ofthe components set forth in the following description or illustrated inthe drawings. The invention is capable of embodiments in addition tothose described and of being practiced and carried out in various ways.Also, it is to be understood that the phraseology and terminologyemployed herein, as well as in the abstract, are for the purpose ofdescription and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the several purposes of the present invention. It is important,therefore, that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The exemplary aspects of the invention will be better understood fromthe following detailed description of the exemplary embodiments of theinvention with reference to the drawings.

FIG. 1 exemplarily shows a block diagram illustrating a configuration ofa queue management system 100.

FIG. 2 exemplarily shows a high level flow chart for a queue managementmethod 200.

FIG. 3 exemplarily shows a queue at a forwarder.

FIG. 4 depicts a cloud computing node according to an embodiment of thepresent invention.

FIG. 5 depicts a cloud computing environment according to anotherembodiment of the present invention.

FIG. 6 depicts abstraction model layers according to an embodiment ofthe present invention.

DETAILED DESCRIPTION

The invention will now be described with reference to FIGS. 1-6 in whichlike reference numerals refer to like parts throughout. It is emphasizedthat, according to common practice, the various features of the drawingare not necessarily to scale. On the contrary, the dimensions of thevarious features can be arbitrarily expanded or reduced for clarity.Exemplary embodiments are provided below for illustration purposes anddo not limit the claims.

With reference now to FIG. 1, the queue management system 100 includesan extraction device 101, a queue examining device 102, a droppingdevice 103, a prioritizing device 104, a Transmission Control Protocol(TCP) Selective Acknowledgments (SACK) device 105, and a multipath TCP(MPTCP) device 106. The queue management system 100 includes a processor180 and a memory 190, with the memory 190 storing instructions to causethe processor 180 to execute each device of the queue management system100.

It should be noted that the forwarder 300 is used in exemplaryillustrations of the invention as a specific type of middlebox. However,the invention is not limited thereto. That is, forwarder 300 refers tonetworking devices such as bridges, routers, and certain types ofnetwork function appliances which are frequently termed middleboxes inthe networking art.

Although as shown in FIGS. 5-7 and as described later, the computersystem/server 12 is exemplarily shown in cloud computing node 10 as ageneral-purpose computing device which may execute in a layer the queuemanagement systems 100 (FIG. 7), it is noted that the present inventioncan be implemented outside of the cloud environment.

FIG. 3 exemplarily depicts a forwarder 300 which has a queue of packetsarriving thereto. FIG. 3 also exemplarily depicts the forwarder 300sending an acknowledgment signal back (i.e., along a reverse path) tothe prior forwarder or device which sent the packets in queue. That is,the forwarder 300 can simultaneously receive packets and send anacknowledgement of the packets along the reverse path.

The extraction device 101 extracts acknowledgement information from thearriving packets arriving at the forwarder 300. Upon receipt of any TCPpacket that contains an acknowledgement, certain information about thepacket is extracted, for example, source and destination IP address,source and destination port number, and ACK number.

The queue examining device 102 examines the incoming queue as comparedto the reverse flow queue of acknowledged packets. Each queue ofoutgoing packets is then examined by the queue examining device 102. Foreach packet in the queue, the packet is examined by the queue examiningdevice 102 to determine if it belongs to a same TCP flow as specified inthe ACK packet of the reverse flow. If true, the data sequenceinformation is determined from the sequence information and the size ofthe data.

The dropping device 103 drops queued packets in the queue if they havealready been acknowledged by the forwarder 300 as determined by thequeue examining device 102. That is, if the data contained in the packethas already been acknowledged by the forwarder 300 (as indicated by theACK), the packet is removed from the queue by the dropping device 103and the memory is returned to the system.

Thus, the dropping device 103 drops retransmitted packets that arewaiting to be queued and are not needed at the forwarder 300, ratherthan other packets which may still be needed.

The invention provides a solution in which information contained inpackets traversing the reverse path may be dropped by the droppingdevice 103 to intelligently select which queued packets to erroneousdrop to solve the problems in which memory can be exhausted, leading todrops of newly arriving packets. These packet drops slow down thecorresponding TCP flows, which consider these drops congestion and slowtheir transmission rates. Response time experienced by the clientincreases, since the delay experienced by the packet (queuing delay) isadded to the total delay of a response, which includes one or morepackets. Senders may unnecessarily retransmit the packet, thereinwasting bandwidth across the network. Delays can adversely interact withTCP retransmission timers, since the sender may believe the packet isdropped when it is in fact delayed.

Thus, as exemplarily shown in FIG. 3, packets 1-3 of FLOW B have beenacknowledged by the forwarder 300 and the acknowledgment has been senton the reverse flow. In this scenario, the dropping device 103 woulddrop FLOW B “packet 2” since this packet has already been received bythe forwarder 300 and is a re-transmission of a previously acknowledgedpacket due to the size of the queue.

The prioritizing device 104 prioritizes the queues to be sent if atriple acknowledgement is seen. That is, while TCP mainly relies ontimer expiration to decide to retransmit a packet that is presumed lost,there are other mechanisms that can accelerate this process. One isknown as a “triple duplicate ACK”. For example, a sequence of packetsarriving at a receiver with the following sender packet sequence is1,2,3,5,6,7. TCP interprets this to mean that packet 4 has been lost.The sender receives acknowledgements from the receiver for packets 1, 2,and 3. When packet 5 arrives at the forwarder 300, the forwarder 300sends another acknowledgement for packet 3 to tell the sender it ismissing 4. This is a duplicate ACK since it is a copy of apreviously-sent ACK. The TCP protocol standard specifies that when threeduplicate ACKs are received, the sender should interpret this to meanthat the subsequent packet has been lost. In the case above, the senderretransmits packet 4.

Thus, the prioritizing device 104 can be used to reduce the time ittakes to retransmit a packet in the following manner. The packetforwarder 300 keeps track of the state of the acknowledgements. When atriple duplicate ACK is seen, the queue examining device 102 can searchits sending queue to see if the required packet (#4 in the case above)is in the queue. If it is in the queue, it can be prioritized by theprioritizing device 104 by moving that packet to the head of the queueso that it is next in line for transmission. This way, the receiver willget the retransmission earlier than if it had been waiting for theactual sender to retransmit the packet. In other words, the prioritizingdevice 104 will prioritize to send a packet if the reverse flow isdetermined not to contain the packet by the queue examining device 102.

The SACK examining device 105 examines SACK blocks to selectively droppackets. TCP includes an option for selective acknowledgements that candistinguish at a finer granularity exactly which packets have beenreceived and which have not. Using the above example, a TCP receiverusing SACK blocks can send a message back to the receiver that says ACK3 SACK 5,6,7. This tells the packet forwarder 300 that packets 5-7 havebeen seen at the receiver and can thus be dropped from the packetforwarder's send queue by the SACK examining device 105.

The MPTCP examining device 106 examines multipath headers to recognizeMPTCP flows, Multi-path TCP (MPTCP) is a TCP-compatible extension thatallows use of multiple paths simultaneously (e.g., both your WiFi andyour Longterm Evolution (LTE) on a cell phone). MPTCP breaks differentpaths into what are called subflows. Two different subflows will lookdifferent at first glance by just looking at the standard TCP and IPpacket headers. However, if the MPTCP header is examined by the MPTCPexamining device 106, the MPTCP examining device 106 can recognize whentwo subfloors are part of the same MPTCP connection, or superflow. Oncethe MPTCP examining device 106 becomes aware of MPTCP, then the MPTCPexamining device 106 examines the queue to see if any redundant data hasbeen sent on a different subflow.

FIG. 2 shows a high level flow chart for a queue management method 200.

Step 201 extracts the acknowledgement information from the arrivingpackets to the forwarder 300.

Step 202 examines the incoming queue as compared to the reverse flowqueue of acknowledged packets. Then, each queue of outgoing packets isexamined. For each packet in the queue, the packet is examined todetermine if it belongs to a same TCP flow as specified in the ACKpacket of the reverse flow. If true, then the data sequence informationis determined from the sequence information and the size of the data.

Step 203 drops queued packets in the queue if they have already beenacknowledged by the forwarder 300 as determined by Step 202.

After step 203, Step 204 prioritizes the queues to be sent if a tripleacknowledgement is seen.

After step 203, Step 205 examines SACK blocks to selectively droppackets,

After step 203, Step 206 examines multipath headers to recognize MPTCPflows.

Step 204, Step 205, and Step 206 can be performed in any order andindependently of one another.

Exemplary Hardware Aspects, Using a Cloud Computing Environment

It is understood in advance that although this disclosure includes adetailed description on cloud computing, implementation of the teachingsrecited herein are not limited to a cloud computing environment. Rather,embodiments of the present invention are capable of being implemented inconjunction with any other type of computing environment now known orlater developed.

Cloud computing is a model of service delivery for enabling convenient,on-demand network access to a Shared pool of configurable computingresources (e.g. networks, network bandwidth, servers, processing,memory, storage, applications, virtual machines, and services) that canbe rapidly provisioned and released with minimal management effort orinteraction with a provider of the service. This cloud model may includeat least five characteristics, at least three service models, and atleast four deployment models.

Characteristics are as follows:

On-demand self-service: a cloud consumer can unilaterally provisioncomputing capabilities, such as server time and network storage, asneeded automatically without requiring human interaction with theservice's provider.

Broad network access: capabilities are available over a network andaccessed through standard mechanisms that promote use by heterogeneousthin or thick client platforms (e.g., mobile phones, laptops, and PDAs).

Resource pooling: the provider's computing resources are pooled to servemultiple consumers using a multi-tenant model, with different physicaland virtual resources dynamically assigned and reassigned according todemand. There is a sense of location independence in that the consumergenerally has no control or knowledge over the exact location of theprovided resources but may be able to specify location at a higher levelof abstraction (e.g., country, state, or datacenter).

Rapid elasticity: capabilities can be rapidly and elasticallyprovisioned, in some cases automatically, to quickly scale out andrapidly released to quickly scale in. To the consumer, the capabilitiesavailable for provisioning often appear to be unlimited and can bepurchased in any quantity at any time.

Measured service: cloud systems automatically control and optimizeresource use by leveraging a metering capability at some level ofabstraction appropriate to the type of service (e.g., storage,processing, bandwidth, and active user accounts). Resource usage can bemonitored, controlled, and reported providing transparency for both theprovider and consumer of the utilized service.

Service Models are as follows:

Software as a Service (SaaS): the capability provided to the consumer isto use the provider's applications running on a cloud infrastructure.The applications are accessible from various client devices through athin client interface such as a web browser (e.g., web-based e-mail).The consumer does not manage or control the underlying cloudinfrastructure including network, servers, operating systems, storage,or even individual application capabilities, with the possible exceptionof limited user-specific application configuration settings.

Platform as a Service (PaaS): the capability provided to the consumer isto deploy onto the cloud infrastructure consumer-created or acquiredapplications created using programming languages and tools supported bythe provider. The consumer does not manage or control the underlyingcloud infrastructure including networks, servers, operating systems, orstorage, but has control over the deployed applications and possiblyapplication hosting environment configurations.

Infrastructure as a Service (IaaS): the capability provided to theconsumer is to provision processing, storage, networks, and otherfundamental computing resources where the consumer is able to deploy andrun arbitrary software, which can include operating systems andapplications. The consumer does not manage or control the underlyingcloud infrastructure but has control over operating systems, storage,deployed applications, and possibly limited control of select networkingcomponents (e.g., host firewalls).

Deployment Models are as follows:

Private cloud: the cloud infrastructure is operated solely for anorganization. It may be managed by the organization or a third party andmay exist on-premises or off-premises.

Community cloud: the cloud infrastructure is shared by severalorganizations and supports a specific community that has shared concerns(e.g., mission, security requirements, policy, and complianceconsiderations). It may be managed by the organizations or a third partyand may exist on-premises or off-premises.

Public cloud: the cloud infrastructure is made available to the generalpublic or a large industry group and is owned by an organization sellingcloud services.

Hybrid cloud: the cloud infrastructure is a composition of two or moreclouds (private, community, or public) that remain unique entities butare bound together by standardized or proprietary technology thatenables data and application portability (e.g., cloud bursting forload-balancing between clouds).

A cloud computing environment is service oriented with a focus onstatelessness, low coupling, modularity, and semantic interoperability.At the heart of cloud computing is an infrastructure comprising anetwork of interconnected nodes.

Referring now to FIG. 4, a schematic of an example of a cloud computingnode is shown. Cloud computing node 10 is only one example of a suitablecloud computing node and is not intended to suggest any limitation as tothe scope of use or functionality of embodiments of the inventiondescribed herein. Regardless, cloud computing node 10 is capable ofbeing implemented and/or performing any of the functionality set forthhereinabove.

In cloud computing node 10 there is a computer system/server 12, whichis operational with numerous other general purpose or special purposecomputing system environments or configurations. Examples of well-knowncomputing systems, environments, and/or configurations that may besuitable for use with computer system/server 12 include, but are notlimited to, personal computer systems, server computer systems, thinclients, thick clients, hand-held or laptop devices, multiprocessorsystems, microprocessor-based systems, set top boxes, programmableconsumer electronics, network PCs, minicomputer systems, mainframecomputer systems, and distributed cloud computing environments thatinclude any of the above systems or devices, and the like.

Computer system/server 12 may be described in the general context ofcomputer system-executable instructions, such as program modules, beingexecuted by a computer system. Generally, program modules may includeroutines, programs, objects, components, logic, data structures, and soon that perform particular tasks or implement particular abstract datatypes. Computer system/server 12 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 4, computer system/server 12 in cloud computing node 10is shown in the form of a general-purpose computing device. Thecomponents of computer system server 12 may include, but are not limitedto, one or more processors or processing units 16, a system memory 28,and a bus 18 that couples various system components including systemmemory 28 to processor 16.

Bus 18 represents one or more of any of several types of bus structures,including a memory bus or memory controller, a peripheral bus, anaccelerated graphics port, and a processor or local bus using any of avariety of bus architectures. By way of example, and not limitation,such architectures include Industry Standard Architecture (ISA) bus,Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, VideoElectronics Standards Association (VESA) local bus, and PeripheralComponent Interconnects (PCI) bus.

Computer system/server 12 typically includes a variety of computersystem readable media, Such media may be any available media that isaccessible by computer system/server 12, and it includes both volatileand non-volatile media, removable and non-removable media.

System memory 28 can include computer system readable media in the formof volatile memory, such as random access memory (RAM) 30 and/or cachememory 32. Computer system/server 12 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 34 can be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable, non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 18 by one or more datamedia interfaces. As will be further depicted and described below,memory 28 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments of the invention.

Program/utility 40, having a set (at least one) of program modules 42,may be stored in memory 28 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment. Program modules 42 generally carry out the functions and/ormethodologies of embodiments of the invention as described herein.

Computer system/server 12 may also communicate with one or more externaldevices 14 such as a keyboard, a pointing device, a display 24, etc.;one or more devices that enable a user to interact with computersystem/server 12; and/or any devices (e.g., network card, modem, etc.)that enable computer system/server 12 to communicate with one or moreother computing devices. Such communication can occur via Input/Output(I/O) interfaces 22. Still yet, computer system/server 12 cancommunicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via network adapter 20. As depicted, network adapter 20communicates with the other components of computer system/server 12 viabus 18. It should be understood that although not shown, other hardwareand/or software components could be used in conjunction with computersystem/server 12. Examples, include, but are not limited to: microcode,device drivers, redundant processing units, external disk drive arrays,RAID systems, tape drives, and data archival storage systems, etc.

Referring now to FIG. 5, illustrative cloud computing environment 50 isdepicted. As shown, cloud computing environment 50 comprises one or morecloud computing nodes 10 with which local computing devices used bycloud consumers, such as, for example, personal digital assistant (PDA)or cellular telephone 54A, desktop computer 54B, laptop computer 54C,and/or automobile computer system 54N may communicate. Nodes 10 maycommunicate with one another. They may be grouped (not shown) physicallyor virtually, in one or more networks, such as Private, Community,Public, or Hybrid clouds as described hereinabove, or a combinationthereof. This allows cloud computing environment 50 to offerinfrastructure, platforms and/or software as services for which a cloudconsumer does not need to maintain resources on a local computingdevice. It is understood that the types of computing devices 54A-N shownin FIG. 8 are intended to be illustrative only and that computing nodes10 and cloud computing environment 50 can communicate with any type ofcomputerized device over any type of network and/or network addressableconnection (e.g., using a web browser).

Referring now to FIG. 6, a set of functional abstraction layers providedby cloud computing environment 50 (FIG. 5) is shown. It should beunderstood in advance that the components, layers, and functions shownin FIG. 6 are intended to be illustrative only and embodiments of theinvention are not limited thereto. As depicted, the following layers andcorresponding functions are provided:

Hardware and software layer 60 includes hardware and softwarecomponents. Examples of hardware components include: mainframes 61; RISC(Reduced Instruction Set Computer) architecture based servers 62;servers 63; blade servers 64; storage devices 65; and networks andnetworking components 66. In some embodiments, software componentsinclude network application server software 67 and database software 68.

Virtualization layer 70 provides an abstraction layer from which thefollowing examples of virtual entities may be provided: virtual servers71; virtual storage 72; virtual networks 73, including virtual privatenetworks; virtual applications and operating systems 74; and virtualclients 75.

In one example, management layer 80 may provide the functions describedbelow. Resource provisioning 81 provides dynamic procurement ofcomputing resources and other resources that are utilized to performtasks within the cloud computing environment. Metering and Pricing 82provide cost tracking as resources are utilized within the cloudcomputing environment, and billing or invoicing for consumption of theseresources. In one example, these resources may comprise applicationsoftware licenses. Security provides identity verification for cloudconsumers and tasks, as well as protection for data and other resources.User portal 83 provides access to the cloud computing environment forconsumers and system administrators. Service level management 84provides cloud computing resource allocation and management such thatrequired service levels are met. Service Level Agreement (SLA) planningand fulfillment 85 provide pre-arrangement for, and procurement of,cloud computing resources for which a future requirement is anticipatedin accordance with an SLA.

Workloads layer 90 provides examples of functionality for which thecloud computing environment may be utilized. Examples of workloads andfunctions which may be provided from this layer include: mapping andnavigation 91; software development and lifecycle management 92; virtualclassroom education delivery 93; data analytics processing 94;transaction processing 95; and, more particularly relative to thepresent invention, the queue management 100 described herein.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

Further, Applicant's intent is to encompass the equivalents of all claimelements, and no amendment to any claim of the present applicationshould be construed as a disclaimer of any interest in or right to anequivalent of any element or feature of the amended claim.

In view of the foregoing and other problems, disadvantages, anddrawbacks of the aforementioned conventional techniques, it is desirableto provide a new and improved queue management system, method, andnon-transitory recording medium that, enables more efficient andintelligent choices in dropping packets to manage a queue.

What is claimed is:
 1. A queue management system, comprising: aprocessor; and a memory, the memory storing instructions to cause theprocessor to execute: dropping a packet in a forward flow queue from aperspective sent from a forwarder to a receiver if the packet in theforward flow queue includes an acknowledged packet in a reverse flowqueue from a perspective sent from a receiver back to the forwarder andreturning allocated memory for the dropped packet to the system;prioritizing a first packet to be sent to the forwarder from the senderif the reverse flow queue from the receiver to the forwarder isdetermined not to include the first packet; Selective Acknowledgments(SACK) examining to examine SACK blocks of the forwarder to selectivelydrop packets in the forward flow queue based on the reverse flow queue;and MultiPath Transmission Control Protocol (MPTCP) examining configuredto examine multipath headers to recognize MPTCP flows and examine thereverse flow queue to determine if redundant data has been sent suchthat the dropping drops the redundant data.
 2. A queue managementmethod, comprising: dropping a packet in a forward flow queue from aperspective sent from a forwarder to a receiver if the packet in theforward flow queue includes an acknowledged packet in a reverse flowqueue from a perspective sent from a receiver back to the forwarder andreturning allocated memory for the dropped packet to the system;prioritizing a first packet to be sent to the forwarder from the senderif the reverse flow queue from the receiver to the forwarder isdetermined not to include the first packet; Selective Acknowledgments(SACK) examining to examine SACK blocks of the forwarder to selectivelydrop packets in the forward flow queue based on the reverse flow queue;and MultiPath Transmission Control Protocol (MPTCP) examining configuredto examine multipath headers to recognize MPTCP flows and examine thereverse flow queue to determine if redundant data has been sent suchthat the dropping drops the redundant data.
 3. A non-transitorycomputer-readable recording medium recording a queue management program,the program causing a computer to perform: dropping a packet in aforward flow queue from a perspective sent from a forwarder to areceiver if the packet in the forward flow queue includes anacknowledged packet in a reverse flow queue from a perspective sent froma receiver back to the forwarder and returning allocated memory for thedropped packet to the system; prioritizing a first packet to be sent tothe forwarder from the sender if the reverse flow queue from thereceiver to the forwarder is determined not to include the first packet;Selective Acknowledgments (SACK) examining to examine SACK blocks of theforwarder to selectively drop packets in the forward flow queue based onthe reverse flow queue; and MultiPath Transmission Control Protocol(MPTCP) examining configured to examine multipath headers to recognizeMPTCP flows and examine the reverse flow queue to determine if redundantdata has been sent such that the dropping drops the redundant data.